1. Technical Field
Exemplary aspects of the present invention generally relate to an image forming apparatus, such as a copier, a facsimile machine, a printer, or a digital multi-functional system including a combination thereof, and more particularly, to an image forming apparatus equipped with a detachably-attachable belt assembly including a belt such as an intermediate transfer belt, conveyor belt, and a photosensitive belt.
2. Description of the Related Art
There has been known an image forming apparatus such as a copier and a printer equipped with a belt assembly. In the known image forming apparatus, four image bearing members, i.e., photosensitive drums are arranged in tandem facing a belt member, i.e., an intermediate transfer belt. Toner images of the colors black, yellow, magenta, and cyan are formed on the respective photosensitive drums. Then, the toner images of each color are primarily and overlappingly transferred onto the intermediate transfer belt, thereby forming a composite toner image. This process is known as a primary transfer process. The composite toner image on the intermediate transfer belt is secondarily transferred as a color toner image onto a recording medium in a secondary transfer process.
In such an image forming apparatus, belt skew of the intermediate transfer belt (for example, displacement of the intermediate transfer belt in its width direction thereof) is corrected by detecting the position (displacement) of the end of the intermediate transfer belt in the width direction.
More specifically, in the known image forming apparatus a detector detects the displacement of the belt member, i.e., the intermediate transfer belt, in the width direction. Based on the detection result, the displacement or belt skew of the intermediate transfer belt is corrected by a correction roller. In this configuration, a connecting member (swingable arm) connected to one end portion of the correction roller around which the intermediate transfer belt is entrained is swingably moved by an eccentric cam, and the other end of the correction roller is fixed so as to change an inclination of the correction roller to correct the displacement of the intermediate transfer belt.
Furthermore, an adjuster for adjusting the fixed end portion of the correction roller is provided to correct more reliably the belt skew of the intermediate transfer belt in the event in which a frame of the belt assembly is deformed or straightness of the rollers around which the intermediate transfer belt is entrained is not sufficient.
Even when the default position of the correction roller shifts off from the center position of the range of movement thereof due to distortion of the frame of the belt assembly and/or insufficient straightness of the rollers around which the intermediate transfer belt is entrained, the adjuster can move the default position of the correction roller towards the center of the range of movement by moving the adjust manually, hence correcting the belt skew.
Although advantageous, in a case in which the belt assembly including the intermediate transfer belt is detachably attachable relative to the main body of the image forming apparatus, the belt assembly may not be installed in the main body of the image forming apparatus with accuracy due to errors in the dimensional accuracy and assemblage accuracy of various parts constituting a support for supporting the belt assembly in the main body of the image forming apparatus, causing a failure in correction of the belt skew by the correction roller and deviation of belt tension of the intermediate transfer belt.
The difficulty described above is not limited to an image forming apparatus using the intermediate transfer belt. The similar difficulty arises in image forming apparatuses using a belt assembly equipped with a belt member such as a transfer conveyor belt and a photosensitive belt.
In view of the above, there is thus an unsolved need for an image forming apparatus capable of reliable installation of the belt assembly without misalignment of the belt assembly, hence preventing a deviation of the belt tension.